The present invention relates to a method of making prefabricated relatively rigid structural panel assemblies, such as prefabricated wall, flooring and ceiling assemblies used by the prefabricated or factory built construction industry, such as the manufactured housing industry. The panels are permanently attached to reinforcing studs, joists or trusses, forming a relatively rigid prefabricated module. Closed wall modules include a pair of parallel panels forming the wall surfaces and a plurality of transverse studs permanently attached to the wall boards.
The method of this invention is particularly, but not exclusively, adapted to a process for making such structural panel assemblies without the requirement of mechanical fasteners, such as nails, staples or screws to secure the panel to the structural members, which must in most cases be covered with batten strips. A problem with the manufacture of prefabricated wall, floor or ceiling panel assemblies has been that the components are not uniform. The boards used for studs, joists and trusses do not have a level or straight plane and may have other discrepancies, such as knot holes. The fibrous panels to which such support members are attached are somewhat flexible, but are often warped. Thus, a wall, floor or ceiling panel, which is supported by studs, joists or trusses attached by mechanical fasteners, is generally both warped and spaced from the reinforcing members in many locations. The exposed surfaces of the mechanical fasteners must also generally be covered. This is to hide fasteners popped out after construction because of inherent assembly and user movement and stresses resulting from the warped components. These problems can only be partially solved in "stick built" construction, where the wall, floor or ceiling panel assemblies are built entirely on site, by selection of materials, the use of shims, etc. However, factory or pre-built construction preferably utilizes mass production techniques which do not lend themselves to such hand-made adjustments.
U.S. Pat. Nos. 4,244,901 and 4,748,781, assigned to the assignee of this application, disclose methods of forming reinforced panel assemblies utilizing polyurethane foam to bond the structural support members to the panels. In the preferred embodiment, the panel is laid upon a flat support surface, the studs or support members are located on the back of the panel and clamped. A high pressure stream of a liquid foamable resin is then directed to the juncture of the support members and the panel, such that the resin foams and fills the space between the support members and the panel, permanently bonding the support members to the panel without mechanical fastening means. This method has been commercially successful in making prefabricated or factory-built structural panels; however this process is not suitable for enclosed panel construction, such as a closed wall structural assembly.
The method of this invention has advantages over the prior art and is suitable for the manufacture of enclosed panel structures, such as closed wall assemblies used by the manufactured construction industry. The disclosed method may be substantially automated and utilizes a relatively small amount of foamable resin adhesive. The method of this invention may also be used at any temperature normally encountered by the factory-built construction industry. Upon completion of the reinforced panel assembly, the assembly can be moved almost immediately using conventional mass production material handling techniques.